How is soil formed?

          Soil is the upper most surface layer of the earth in which plants grow and on which directly or indirectly, all life depends. It is composed of rocks, minerals, organic matter, water and air. It did not take one or two days for the soil to form but millions of years. Do you know how soil is formed?

          Millions of years ago, soil existed in the form of rocks. Since then weather and other natural forces like wind, rain, snow, water, heat etc. had been interacting with the rocks to break them into smaller fragments. These forces further converted the rock-pieces into sand. Bacteria, carbonic acid and other micro-organisms converted this sand into soil. In course of time bacteria converted the bodies of dead plants and animals also into soil.

          Soil is classified according to its colour, texture, chemical properties and climate. Colours of soil range from yellow and red to black. Soils are also categorized as acidic, alkaline and neutral. Extremely acidic or alkaline soil does not support plants. 

          There are three main types of soil a) Pedalfers - associated with temperature, humid climate, contain iron and aluminium salts, b) pedocalo - associated with low rainfall regions, contain soluable substances such as calcium carbonate and other salts and c) Laterites - tropical red or yellow soils heavily leached and rich in iron and aluminium. Based upon soil classifications, modern farming and plantation are made to yield maximum returns.

          An organic matter called humus is constantly being added to the parent soil. Humus makes the soil more fertile.

          Deep, well developed soil is divided into four layers called horizons. The top layer, where most plants grow, is called the A-horizon or top soil. This layer is rich in organic material and contains some minerals. The next is called B-horizon or sub soil. It is rich in minerals, especially in clay, but with little or no organic matter. Farmers often mix the A-and B-horizons by ploughing. The third is called C-horizon and it is a layer of weathered and shattered rocks. It is called the fragmented rock. It is quite similar to parent soil. The last layer is D-horizon or bed rocks. 

Does a black cat bring bad luck?

          Many people all over the world regard the sight of a black cat as inauspicious. If a cat crosses our path, we take it as a bad omen. Do you know why a cat in general and a black cat in particular are considered inauspicious?

          In fact, it is nothing but superstitious to consider a cat inauspicious. This superstition goes back to a belief of thousands of years. The ancient Egyptians worshipped the cat. They had a goddess called Pasht whose head resembled that of a cat. They believed that this goddess had nine lives. Whenever a black cat died in Egypt, its dead body was preserved as a mummy (preserved corpse of a human being or animal). Remains of thousands of black cats have been recovered from a cemetery of Egypt. Killing a cat was then considered as an offence, punishable with a death sentence. Thus people had a great fear of the sight of a black cat.

               During the middle ages witches and witch doctors always used the skull of a black cat to prepare mysterious medicines. As a result people started thinking that a black cat was a bad omen. Thus people have been suffering from this superstition for many centuries. The truth is that no cat is inauspicious. The cat is a pet animal that was domesticated about 5000 years ago. 

Why do objects appear coloured?

          Do you know why an apple or tomato appears red, the grass green, and the milk white when they are all illuminated by the same sunlight? In fact, the colour of an object depends upon the colour it reflects.

          The sunlight which appears white comprises of seven colours: violet, indigo, blue, green, yellow, orange and red. In sunlight, an apple or tomato appears red because it reflects only the red colour and absorbs the rest.

Grass appears green because it reflects only the green colour and absorbs all other colours present in the sunlight. A white shirt or milk appears white because it reflects all the colours of the sunlight. And a blackboard appears black because it absorbs all the colours of white light and reflects none. To prove this, focus red light on a white shirt and you will see that it becomes red. White objects take the colour of light falling on it. Similarly if we see an apple in red or white light it will appear red but in green or blue light it would appear black. It cannot reflect any other colour but red and, therefore, looks black in any other colour except red or white. This is how the various objects get their colour. 

Which planets have satellites?

          The heavenly bodies that revolve round the sun are called planets. There are nine planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The bodies revolving round these planets are called their ‘satellites’ or ‘moons’.

          Scientific investigations made so far have revealed that all planets do not have satellites. For example, Mercury and Venus do not have any satellite. Earth has 1 satellite - the moon. Mars has 2 satellites and the Jupiter has 16. The number of the moons revolving round Saturn is 24. The Uranus and Neptune have 15 and 6 satellites respectively. Pluto has 1 satellite.

          The size of different satellites is different. There are some satellites which are bigger than moon. The diameter of two satellites of the Mars, Deimos and Phobos, and the outer satellites of the Jupiter, Ganymede and Callisto are as big as Mercury and Mars. The diameters of Titan and Triton - the satellites of Saturn and Neptune are 5150 kms and 2700 kms respectively and more than the diameter of our moon.

          Except Titan, all the satellites have small force of gravity. As such none of them has any atmosphere. Because of low temperature at Titan, it has an atmosphere consisting of methane and hydrogen. But there is no life on this satellite.

          As yet we have not come across any satisfactory theory regarding the origin of the satellites. However, it is believed that their origin is similar to that of our solar system.

How does a currency counting machine work?

          There are thousands of banks in the world where currency notes are counted and packed in the denominations of hundreds. Job of counting and packing is done by a large number of people. The job of counting the currency notes is quite boring. Scientists have developed a machine which automatically counts and packs the currency notes. This machine is a wonder of electronics.

          Working principles of a currency counting machine is shown schematically in the figure. The bundle of notes to be counted is placed on platform P-1. These notes are pushed in the forward direction by a feeding roller R-1. These notes are counted by a sensor S-1. Thereafter the notes pass through the rollers R-2 and R-3 and channel C-1. Through the channel the notes reach the sensor S-2. In case of any error in counting, S-2 will shut the motor automatically and display the mistake. After sensor S-2, rollers R-4 and R-5 pick up the notes and throw them into the slots of the centrifuge roller. These notes are released as they reach the platform P-2 and start stacking upon it. This platform is equipped with another sensor S-3 which indicates whether P-2 is empty or loaded.

           It is a microprocessor based machine and hence its reliability is very high. These machines can not only count currency notes but also the coins. These are portable machines and can be installed anywhere. Nowadays these machines are being used by many banks.

What are pain relievers?

          A pain reliever is a drug that reduces pain without causing unconsciousness or complete loss of feeling. In medical terminology, they are called analgesics. There are two main types of analgesics: The peripherally-acting analgesics or non-narcotic pain-relievers and the centrally acting analgesics or narcotic pain-relievers.

          The first type acts on any pain associated with muscles or bones or their related structures. Hence these are called peripherally-acting analgesics or ‘mild analgesics’. The most common of these is aspirin. Its active constituent is acetylsalicylic acid. It was first synthesized in 1899, and produced in huge commercial quantities ever since. Other analgesics of this group include analgin and paracetamol. These are used to relieve headaches, rheumatism and other body pains.

          The second groups of pain killers, the centrally-acting analgesics are very potent drugs and include substances derived from opium, an extract of the poppy plant. Two such analgesics are morphine and heroin. In the brain they depress the activity of the cortex, and thalamus which is the part that receives messages from the body’s pain receptors. They are very effective and act instantly when injected into a muscle or vein. They are only used by physicians for relieving intense pain of those suffering from cancer, heart attack or severe injuries involving broken bones or wounds. Some common drugs of this group are Codeine, Pentazocine and Ethoheptazine.

          Both types of analgesics have a number of side effects. For example, aspirin can irritate the stomach, cause indigestion or in serious cases it may even lead to an ulcer. If used indiscriminately, it may cause anaemia.

          Morphine drugs can cause nausea and vomiting, but this side-effect can be blocked by giving the drug Cyclizine along with it. Morphine and its allied drugs can cause addiction when used over a prolonged period.

          Some other analgesics such as antipyretics are used to bring down fever. In severe cases or while carrying out a surgical operation, doctors apply many anaesthetic drugs to deaden pain.

          These drugs are available under different brand names. Aspirin is available in the brand name of Disprin, Mejoral etc.; paracetamol is available in the name of Calpol, Crocin etc. Novalgin is an analgin whereas Fortwin is a brand of Pentazocine. It is always advisable to check the constituents before buying these drugs. 

Why do giraffes have a long neck?

               Giraffe is the tallest land animal in the world, but scientists are unable to explain how it got its long neck. A famous French zoologist, Jean Baptiste de Lamarck, proposed a theory that at one time giraffe’s neck was much shorter than what it is now. It had to raise its neck to eat the leaves of the trees. According to Lamarck, the part of the body which is used most develops most. The giraffe had to raise its neck time and again to reach the upper branches of trees when the leaves on lower branches were eaten away. This excessive use of the neck resulted in its gradual increase. The successive generations of the giraffe started having longer necks and finally today’s long-necked giraffe emerged.

               The male giraffes grow upto a height of 5.5 m and weigh more than 1, 000kg. It is an herbivore. It chews its food in spare time. The formation of giraffe’s body is such that its mouth can easily reach the leaves of high trees. Its tongue is about 45 cms long and so constructed that it can even eat the leaves of thorny plants. Its upper lip is long which helps it wrench off many leaves at a time.

               The colour of giraffes resembles the shadow of the trees and as such it is not easily visible to its enemies. It is usually yellowish-brown. Its ears are very sensitive.

               It can hear the faintest sounds, but it is nearly incapable of uttering sounds. The word ‘nearly’ has been used because some of the female giraffes and their young ones have been found mowing like cow or ox in the zoological parks but most of them do not utter sounds. The reason for this inability lies in the underdevelopment of its voice box or larynx. Probably due to this reason, it has a keen sense of smell and sight. If attacked, it can run at a speed of 45 kms per hour for an extended period of time without tiring. As far as fast running is concerned, it can beat even the fastest of horses. When it is attacked by some other animal, it retaliates with the help of its head and hind legs. As its eyes are far above the ground, it can easily see predators long before they can get close enough to attack. That is why even the lion has to be very cautious while attacking a giraffe. Lion always attacks it from behind because giraffe strikes with its head like a hammer.


What is a flying fish?

          There is a kind of fish which can glide like a glider. It is called a ‘flying fish’. It does not fly like birds, because it has no wings. It first swims very fast on the surface of water up to a speed of about 65 km/hr and then spreads its front fins and starts flying in the air. The fins remain spread firmly during the flight with the help of its muscles. But as soon as it lands on water, they shrink to their original position.

          The most common flying fish is the two-winged type, which is found in all tropical seas. It is about 25 cms long. The largest flying fish is about 45 cms long and has four wings. It lives off the coast of California. The length of flying fishes varies from 5 cms to 45 cms. Sometimes while flying it dashes against the water waves. At that time it looks very beautiful. The collision with waves gives it extra energy and it can further fly up to greater distances. It usually flies quite high in the air. A flying fish can glide for over half a minute. 

How fast can marine animals swim?

          The sea abounds with different kinds of living creatures such as fish, tortoise, crocodile, eel, dolphin, whale, etc. Do you know with what speed these animals can swim? 

          The sailfish swims the fastest amongst all the aquatic animals with a speed of up to 110 kms per hour. Next is the sword fish with a maximum speed of 95 kms per hour. The tunny and the rainbow trout can swim at a maximum speed of 75 kms per hour. The speed of dolphin goes up to 65 kms in an hour.

          Besides these, the swimming speed per hour of some other aquatic animals are: tarpon, 55 kms; shark, 45 kms; trout, 35 kms; salmon 25 kms, eel, whale and pike, 15 kms. Cray fish, carp, tench, perch, octopus, etc. swim at a speed of less than 10 kms per hour. These are not the normal speeds but are the maximum recorded speeds of sea animals.  

What is a Silicon Chip?

          The microchip or silicon chip has completely changed the colour of the electronic world by providing a new direction to it. It has led to the invention of electronic calculators, personal computers, digital watches, microwave ovens etc.

          The silicon chips are tiny crystals of silicon which contain large number of electronic components. Silicon is the most abundant element on earth as the crust of the earth is largely made of silicon. But silicon is not found in a free state as it is always combined with one or more additional elements. In one sq. cm. chip, about one million electronic components can be squeezed. The size of a chip is smaller than our finger tips. They can be made to carry very small electrical circuits, called microcircuits. These are used in transistor radios, digital watches, calculators and computers. They can be used in small electronic devices as the chips are very small.

          But how is silicon chips made? Silicon chips are made from a single crystal of silicon. Thin wafers of about 0.5 mm thick are sliced from a single crystal. One side of each wafer is first polished and then oxidized in a furnace: The disc is covered with a layer of photo resist material and then exposed to ultraviolet light through the clear sections of a mask. A light sensitive coating is developed and the exposed areas are dissolved away by the solvent. Unexposed areas are not affected so a pattern remains identical to the mask. The exposed areas are etched in hydrofluoric acid. Another solvent removes the resist. In a furnace, the wafer is exposed to chemicals which penetrate the silicon through the oxide gap to make transistors. The process is repeated several times. The wafer is coated with aluminium and a final layer of metals connects the components together. After careful inspection, chips are selected and released for use.

          Nowadays microchips are being used in electronic sewing machines, washing machines, word processors, and so on. 

What is a space suit?

          We know that the atmosphere at the Earth’s surface produces a pressure equal to the weight of a large automobile on each square metre. We do not notice this since it is equal both inside and outside our bodies. But if the air inside a metal pot is, for instance, forced out by boiling water inside it, the pot collapses under this pressure.

          Similarly, an unprotected astronaut in a space flight would not only die by swelling up, but his blood would also start to boil. The temperature at which a liquid boils depends on the atmospheric pressure. At a height of 9 km, water boils at 74°C; and above 19 kms, blood boils below body temperature. At zero pressure, the astronaut’s blood would instantly turn to deadly foam.

          Therefore, keeping these aspects in view, a space suit is specially designed so as to protect an astronaut from the dangers of space during space flights. Space dangers include extreme temperature, hazardous radiations, fast moving particles, vacuum etc.

          Space suit clothing is made of several layers each of which has a specific purpose. One of the inner layers controls the temperature. With the help of this Manned Manoeuvring Unit (MMU), an astronaut can leave the space craft and fly independently. It has the provision for oxygen gas. Each suit has got a primary life support system. It holds enough water and oxygen to enable the astronaut to carry out space walks for several hours. The space suit has the liquid cooling and ventilation system. In fact each suit is made from a number of different pieces. Each piece is made by selecting the sizes. Individual astronaut is given a suit from these so as to fit him.

          One very surprising thing about MMU is its weight. On earth it weighs about 158 kgs but when used in space it makes the astronaut very mobile. This is because of the weightlessness conditions in the space.

          A space suit therefore is a life-saving device for an astronaut.


Which animals resemble man?

          Gorilla, chimpanzee and orangutan are some of the animals which resemble man many respects. They are a kind of monkeys without a tail. They fall under the ‘anthropoid’ category and are found in the dense jungles of Africa and Asia.

          Among these animals, chimpanzee has the closest resemblance to man. In fact, the bone structure of all these animals has many similarities to that of man. The number of their teeth and their constitution are similar to ours. Like human beings, they too have wrinkles on their forehead. Their skulls are also like ours. Even their blood is similar to ours. However they cannot speak like us. They eat blossoms, leaves, stems, fruits, insects and bird’s eggs. 


          Gorillas are generally as tall as human beings, but heavier and stronger. They live in groups of 20 to 30. The young ones live with their parents till they become adults. Young gorillas sleep on trees, while the adults, on the ground. They are generally peace-loving animals, but once teased or wounded, they start beating their breasts. They can produce a drumming sound from their mouth. Their skin is black.



          Chimpanzee is the cleverest of all these animals. It can imitate many habits of man. Its body is covered with black hair. It can be easily captured.

          Unlike gorilla and chimpanzee, the orangutan is almost completely arboreal. It has bony crests over the top of its skull. Its forehead is higher than that of gorilla and chimpanzee. The lips protrude and the ears are small. All these animals belong to the group to which we belong.


How is the distance of stars from the earth measured?

          The stars which we see shining at night look very attractive and bright. Some stars look brighter than others. This is so because their sizes and distances from the earth are different. These stars are billions of miles away from our earth and shine with their own light. Do you know how the distance of stars form of earth is measured?

          Scientists have evolved a simple technique to measure the distance of the nearby stars. Suppose we want to measure the distance of a particular star ‘C’. We take its photograph from a place ‘A’ on the earth. After six months, the earth is at the position ‘B’, since it is revolving round the sun. We now take another photograph of the same star from the position ‘B’. A comparison of the two photographs will show that ‘AB’ is the diameter of the earth’s orbit round the sun and is equal to 186 million miles. Now the angle ‘ACB’ is measured. With the help of these two figures, the distance of the star ‘C’ is measured. This is known as the method of triangulation.

          Using this technique, the distance of many stars has been measured. The distance of Alpha Centauri from earth has been found to be about 4.35 light years. The distance of the Sirius has been determined to be 8.48 light years. However, this technique is not suitable for measuring the distance of very distant stars. The distance of such stars is determined on the basis of their brightness or colour. The most widely used system for measuring the distance of stars is the two-dimensional classification method developed by J.M.Johnson and W.W. Morgan. This system is based upon photoelectric measurement in three wavelength bands in ultra-violet, blue and yellow (or visual) regions of spectrum. This method is known as UBV system. Scientists have succeeded in measuring the distance of stars as far away as 8 million light years from the earth.


How can we test the purity of milk?

             The instrument used to assess the purity of milk is called a ‘lactometer’. It is a cylindrical vessel made by blowing a glass tube. One end of the glass tube is blown in the form of a bulb and filled with mercury. The other end is blown in the form of a thin tube and sealed. For calibration it is dipped in pure milk. The point up to which it sinks in the pure milk is marked ‘M’. After that it is put in water and is marked ‘W’ at the point up to which it sinks in water. It sinks less in milk than in water because milk is denser than water. The portion between ‘M’ and ‘W’ is divided into three parts and marked as 3, 2 and 1 to indicate the level of purity.

              Whenever we want to test the purity of milk, the instrument is put in milk. If it sinks up to the mark ‘M’, the milk is pure. If the milk is not pure, but mixed with water, it would sink to a mark higher than ‘M’. When the instrument stands at the mark 3, the milk is 75% pure. At the mark 2, the purity is only 50%. Mark 1 indicates a purity of 25%.

            Even though lactometer is commonly used to measure the purity of milk, yet, it is not a very reliable instrument. It has been observed that in the case of skimmed milk (denser than pure milk) that the lactometer fails to give the correct assessment of the purity, if the density of the skimmed milk is made equal to that of the pure milk by adding water in an appropriate proportion.

What is Paging Service?

            The 21st century would take people to a world of mechanical solidarity with courtesy from services like paging service, cellular telephone and Internet etc. Having acquainted ourselves with services like cellular telephone and Internet earlier, now let us discuss what paging service is all about.

            Paging is a one-way wireless communication providing instant access to the person being paged. One-way communication means that the subscriber only receives the message and can not communicate back instantly. The subscribers receive messages from anyone with access to a telephone. The modus operandi is as follow: The paging network of a particular region is co-ordinated by a ‘pagers exchange’ or network operator. Subscribers have a paging number assigned exclusively to them by the concerned network operator. The person who wants to send a message to a subscriber rings up the operator and leaves the message with him along with the subscriber’s paging number. Then the operator relays the message to the subscriber either directly or through any other regional operator. The message is then received by a small palm-size device called ‘pager’ kept by the subscriber with himself. An alarm sound from the device alerts the subscriber who then reads the message, flashed on the screen of the device. Some pagers also vibrate to alert the subscriber of an incoming message. The main advantage which a pager provides is that the subscriber receives the message wherever he may be since he carries the wireless device (pager) always with him.

            In India, as of now, the government has issued licenses to private operators to provide paging service to interested people and the number of subscribers is growing fast. As per current estimates, the running cost of a pager for monthly service would be around a couple of hundred rupees and a pager, at the moment, costs about a few thousand rupees. It is now the cheapest and most reliable one-way communication system available in the market today. Although its primary use is to get a message across fast, it has other potential uses such as getting across share market information by the business circles or to have latest cricket scores, for instance. The only demerit is that it provides only one-way communication as the receiver can not communicate back to the caller.